The Tabard Inn has a beautiful garden and good food. The Reef has some rooftop dining, I forget how good the food is, it has been a while. Lauriol Plaza has rooftop dining, people think it is crowded, and I don't think their mexican dishes are the best their, but they have some great cuban/ salvodorean dishes. I thought there was a place with a glass rooftop near 14th and U, but I forget what it is. I think I would choose Tabard.

One of the most beautiful summer dining spots in DC is the outdoor courtyard at Tabard Inn. It's really beautiful, romantic, and relaxing. When you make your reservation make a special request to be seated outside.

I hear Perry's has good food and a great roof top deck but I've actually only seen it from the street. But it looks nice with little lights etc. (Bonus: my coworker who is a vegan said he found plenty to eat there!)

Also in Adams Morgan is the Reef (which can get very crowded on the weekends, I suggest going during the week) and Bourbon has a back deck area (not facing the street).

Tabaq has a great rooftop dining area, although I personally like their drinks more then their food. Brunch is ok there.

There is a lovely rooftop patio at Straits of Malaya, right near Lauriol Plaza. It is "on the street," but because of the height, it is not loud or busy-feeling. Tabaq's rooftop deck (U Street) offers great views but be warned that tables are extremely close together. The roof of Marvin (U at 14th) is great but I don't think food is served there - only drinks. The patio at Poste in Penn Quarter is stellar. If you want really casual food, the atmosphere at Cantina Marina on a sunny weekend afternoon is boisterous and fun.

Tabaq around 14th and U has a spectacular glass encased rooftop with endless views of DC. mediterranean tapas, and spectacular drinks... of course i'm a simple "vodka and-" girl, so if you are info fancy cocktails, my opinion on the drinks won't matter to you! :) several very nice import beers as well- never had the wine. tapas are tip top- we've enjoyed every outing we've ever had here. the menu has expanded to include brunch- we will be back soon!